Unless otherwise indicated herein, approaches described in this section are not prior art to the claims listed below and are not admitted as prior art by inclusion in this section.
High-efficiency video coding (HEVC) is the latest video coding standard developed by the Joint Collaborative Team on Video Coding (JCT-VC). In HEVC, a coded picture is represented by a plurality of coded slices. Each slice is partitioned into non-overlapped coding tree units (CTUs). The size of a CTU is specified by a syntax element in the sequence parameter set (SPS) and ranges from 16×16 to 64×64 in the main profile. A CTU can be further partitioned into one or multiple coding units (CUs) to adapt to varying local statistical characteristics. Each CU can be further divided into one or multiple prediction units (PUs). The PU works as a basic functional unit for predicting sample values in a block region. After obtaining the residual block by a prediction process, a CU can be further partitioned by a residual quadtree structure into one or multiple transform units (TUs). The TU is a basic block for applying transform and quantization operation for representing the prediction residual signal from a picture block region. A TU can consist of multiple transform blocks (TBs), corresponding to different color components from a TU block region.
Joint Video Exploration Team (JVET) of ITU-T SG 16 WP 3 and ISO/IEC JTC 1/SC 29/WG 11 is currently conducting research on the next-generation international video coding standard. In Joint Exploration Test Model 5 (JEM5), a quadtree plus binary tree (QTBT) structure is utilized for partitioning a CTU into one or multiple CUs. Each CU contains only one PU and one TU. The resulting TB dimension can range from 128×128 to 2×2 and can take a square or rectangular shape. In an I-slice, each CTU can be partitioned into two separate coding trees for one luma component (Y) and two chroma components (Cr and Cb), respectively.